Washington Post: Little by little, ABC’s “World News Tonight” has climbed to the rocky summit of Mount Nielsen. After years of also-ran status, the evening newscast has caught up to NBC’s “Nightly News,” the ratings champ for more than five years. The two programs now jockey for the title of America’s most-popular TV news source. How did that happen? The venerable broadcast has slowly evolved into a newscast engineered for the social media age. In important ways, “World News” looks and sounds different from its competitors. It’s brighter, tighter and indeed quite a bit lighter than its evening rivals.